1. Field of the Invention
The present invention relates to a method of manufacturing rims for motor vehicles, and more particularly to a method of manufacturing the rims of disk wheels for motor vehicles capable of helping reduce road noise.
2. Description of the Related Art
It is already known that, in a tire for motor vehicles, road noise is aggravated by columnar resonance in the airfilling area (closed space) formed between the inner circumferential face of the tire and the outer circumferential face of the disk wheel rim. This is due to the phenomenon that the resonance of the airfilling area formed by the tire and the rim is kept constant irrespective of the revolutions of the tire, and the resultant vibration at a constant frequency in the same direction is added all the time, because the airfilling area has the same cross-sectional area in the circumferential direction of the tire.
As a method to restrain this aggravation in road noise, there is disclosed in JP-A-11-245605 a method intended to reduce road noise by fitting a plurality of movable shielding plates in the rim well part, so that these shielding plates be erected upright by the centrifugal force during the running of the vehicle to partition the airfilling area and thereby to shift the frequency of columnar resonance to a vibration frequency region in which no road noise problem can arise. This will be referred to as the First Case of the related art.
On the other hand, JP-B2-3003478 discloses a technique that a flexible ring on which a plurality of bulkheads are formed to partition the airfilling area is inserted into the inner space of the tire to reduce road noise as attempted in the above case. This will be referred to as the Second Case of the related art.
In both of the first and second Cases of the related art, an element separately formed from the disk wheel, such as shielding plates or a flexible ring, is fitted thereto. Thus, this invites an increase in cost and, moreover, the first Case involves the risk that the tire, when it is fitted, may strike against the shielding plates and break them.